A conventional writing pen comprises a liquid storage portion and a liquid guiding portion at least; the liquid storage portion is configured for storing liquid ink, even gel ink as a source of ink; and the liquid guiding portion leads ink to a nib for a writing purpose. As the writing pen is used, and ink is consumed, the liquid storage portion needs a supplement of air outside, in order to prevent the liquid storage portion from generating negative pressure which affects a flowing out of the ink. That is, an air flow channel should be arranged between the liquid storage portion and outside atmosphere to make the air pressure of the liquid storage portion equal to the air pressure of the outside atmosphere, which is a key technology to ensure that the writing pen writes smoothly and is not easy to leak.
In an existing technical document, a reservoir type writing pen is provided, and the writing pen adopts a dust proofing plate, a labyrinth vent plug, a nano lyophobic infiltration plate and a one-way valve to achieve a connection between the liquid storage portion and the outside atmosphere. Although the writing pen of this type can keep air pressure balance, however, the writing pen has a complex structure, comprises a lot of parts, has many assembly steps and a high cost.
In another existing technical document, a reservoir type writing pen is provided, and the writing pen adopts a nano lyophobic infiltration plate to achieve a connection between the liquid storage portion and outside atmosphere. However, the writing pen also has a complex structure, comprises a lot of parts and has many assembly steps, which is not suitable for an automatic production.